Brown the butter: Melt ¾ cup of unsalted butter over medium heat for 5–7 minutes until golden brown.

Combine sugars: Mix cooled brown butter with dark brown sugar and white granulated sugar using an electric mixer for 1–2 minutes.

Add eggs and vanilla: Incorporate 1 egg, 1 egg yolk, and 2 tsp vanilla extract; mix until smooth.

Mix dry ingredients: Whisk together 1¾ cups flour, ¼ cup espresso powder, ½ tsp baking soda, and ½ tsp sea salt.

Blend wet and dry: Gradually fold dry ingredients into wet until just combined.

Add chocolate: Fold in 4 oz chopped dark chocolate until evenly distributed.

Chill the dough: Cover with plastic wrap and refrigerate for at least 30 minutes.

Preheat oven: While dough chills, preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.

Scoop and bake: Scoop 1-ounce balls of dough onto baking sheet, bake for 11 minutes until edges are golden brown.

Cool cookies: Allow cookies to rest on baking sheet for 5 minutes before transferring to wire rack.